Device for adjusting the pitch of air propellers



July 23, 1946. R. PRAUSE DEVICE FOR ADJUSTING THE PITCH OF AIRPROPELLERS Filed Oct. 22, 1940 s Sheets-Sheet 1 July 23, 1946. p us 72,404,743

DEVICE FOR ADJUSTING THE PITCH OF AIR PROPELLERS Filed Oct. 22, 1940 5Shets-Sheet 2 gi 'nz 0 32 H 2. 3 37 1o 33 a 3 7 -s ezssz; m

1 3 I j J 2 066? 7 rd u e July 23,1946. IR. PRAUSE 2,404,743

DEVICE FOR ADJUSTING THE PITCH OF AIR PROPELLEBS Filed 001:. 22, 1940 5Sheets-Sheet 3 Inventor:

fiber 7 Pl'a, Q66

Patented July 23, 1946 UNIT-JED STAT-ES PATENT OFFICE Robert Prause,Augsburg. Germany; vested in the Alien"Property Custodian ApplicationOctober 22,1940, Serial-No.36 2;279 .Infiermany June. 10, .1938

llllaim. This invention relates to 'apropeller adjustment device.

Certain devices for theadjustment of the pitch of air propellers whilein operation areknown in which the blade adjustment is carried out bymeans of a bushing'or sleeve mounted to slide on the propeller shaft.The sliding operation of said bushing or sleeve is effected by means ofan adjusting lever or traverse which surrounds the bushing and at oneend is mounted to swing on a stationary point of the aeroplanethe otherend being connected by a simple link with an adjustable system of rodsleading tothe pilots seat. The sliding motion receivedby the slidingbushing is transferred to the base of the propeller blades, which areturnably mounted, by means of jointed levers. Although this known deviceenjoys the advantage of great simplicity as compared with other designsof blade adjustment, it has not proven useful in actual practice. It wasfound that the suspension arrangement which allows the adjustmenttraverse surrounding the sliding bushing'to swing around one axis only,or around two parallel axes, showed considerable wear and tear,especially at the sliding bushing,

after only a few flying hours.

It is an importantobj'ect of the present invention to provide means inthe adjustment device for avoiding such premature wear. In the course ofthe investigations leading'to the present invention it has been foundthatthis defect of-the known device'is 'mostlytdue to thefact that .thepropeller shaft and the axis'for the swing adjust ment of the traversewhile in operation deviate imperceptibly from their original position atright angles to each other. Such deviation is brought about by certainforces during the flight. The relatively rigid connection of theadjustment traverse on one side and the play of the parts'be longing tothe adjustment device on the otherside tend to cause a sort of wabblingmotion ofthe traverse ring, or of the sliding bushing, causing thelatter to deteriorate and to wear out "rapidly, since the adjustmenttraverse owing to its rigid connection cannot give way "to theoscillating movement. Moreover, the sliding motion of the adjustmentsleeve causes an edgewise pressure stress which, in cooperation with thewabbling motion, tends to wear out the sliding bushing.

"Therefore, the present "invention has for its object to provide aconstructionof a-propeller adjusting *device which permitswabbling-mot'ion of the parts without any substantial wear. With theseand further objects in view, :as may be- .2 come apparent from aconsiderationottheyannexed drawings and the following description, theinventionconsists not only inthe structures hereinpointed out andillustrated bythe idrawings, but includes .furtl-rer r-structure-scoming within the scope of the claim. 7 r

The character of the invention. however, .may be best understood byreference .to certainofsits structural forms, .as illustrated .by,thenaccom panying drawings in which: V V l Fig. 1 shows a schematic,perspective-viewof the essential parts of an adjustment ,device'havingthe invention applied thereto. w 1

Fig. 2is a side elevation, partly in sec ion, .of the same adjustmentdevice. i

Fig. 3 is a plan view,;partly in section, online III-III of *Fig. '2. gj

Fig. 4 is a section accordingto line IV-.-IV of Fig. 2.

Fig. 5 1s a-section-similar.toFig. 4, but shoW- ing another design-ofthe gimbal mountingof the adjustment device.

As here shown, I provide means between the stationarypoints for thesuspension of the device and the sliding bushing or sleeve forgpfirmitting a Cardan motion, or relative swinging of the parts aroundtWo axes at right anglesto each other. The traverse lever foradju'sting'the sliding bushing is suitably designed as a ringsurrounding the .bushing. Said ring at one end is mounted at astationary point of the aeroe plane, preferably by means of .a link orswing member, so as to. move around two perpendicular axes, :while at.its :other end .the adjustment spindle is connected, movable, alsoaround two perpendicular axes, bymeansof the spindlenut. The annulartraverse lever Whichsu-rroundsi-the sliding bushing and the propellershaftis connected with the sleeve'eifecting the blade adjustment by mean.of a ball bearing .whichlpreferably is of a type to receiveaxialforces. The traverse ring is swingably connected with :the outeruring,or with thesupporting ,ring "for the ball bearingby means of trunnions.

By arranging the component partsor elements, as above described, which.make possible a gimbal movement of the adjustment sleeve, greatimprovement in the stress conditions tofithenidjustment device has "beenobtained and, as ;:a consequence, the number of "flying ahonrs could beconsiderably increased. Preferably, andxas here shown, I may obtain afurther improvement of the stress conditions by manufacturing. theadjustment sleeve and/or -a sliding bushing mounted on the propellershaft "fromsynthet'ic material, especially synthetic resin with textileinserts or admixtures. This material may consist of various kinds ofsynthetic compressed material such as phenol-aldehyde condensationproducts which are known as Bakelite. Also resin impregnated fabrics,hard wood and hard paper of all sorts as well as any pressing materialfrom' paper and textiles in layers in nonlaminated form may be usedafter having been treated with a suitable binding substance. The

sliding bushing mounted on thepropeller shaftcan be made of suchsynthetic material, while; the sleeve moving thereon can be madeofmetal. a By manufacturing the bushing and/or lsleeve from any of thesynthetic materials mentioned,

threaded rings "21 and 28, the first ring being screwed together withthe traverse ring I4 and serving as a frame for the ball bearing 24,while a longer life of the device isobtained than would. y

be the case if it would be manufactured exclusively from metal or metalalloys. vEven if metal alloys of the highest abrasion resistance areused in the manufacture of said bushing and sleeve, undesirable quickwear have been-found to be unavoidable. Applying the experience so farmadewith slide bearings of artificialmaterial, it was surprising to findout that by using synthetic material in 'the'device, according to theinvention, the dangerous stresses at the edges of the sleevecould bemet. 7

Referring now'to the drawings in greater detail, and firstto Figs. l'tol, it "will-be seen that the propeller blades land 2 of a two bladepropeller are tu'rnably mounted in the propeller hub 3. The hub '3 iscoupled. with a hollow propeller shaft 4 by means of 'two mutuallyengaged toothed portionsindicated at 5, both parts being held togetherby a threaded member 6. The propeller shaft 4 at its other end is shapedto'fit thedifierent motor connections and is connect- ,ed with the motorshaft by bolts I. An antifriction bushing or sleeve 8 consisting of"synthetic resin on a phenol-aldehyde basis with textile admixtures isfastened on the hollow shaft 4 by means of screw bolts 9, for receptionof an adjustment sleeve I mounted to slide on the bushing 8, andprovided with eyelets II which have the guide members I2 jointed to themfor connection with adjustment levers I3 which are rigidly screwed tothe base of the propeller blades by means of their female thread so thatany swinging of, the levers I3 will also cause the. pror peller' bladesland 2 to be turned correspondingly. The adjustment sleeve I 0 issurrounded bythe ring-shaped adjustment traverse lever I4 which at itsextreme opposite ends I and II i connected by means of a Cardan oruniversal joint to connecting members which in turn are suspended attationary points of the aeroplane. The connection at II is adjustable insuch a Way that the traverse ring duringthe adjustment can beswungaround the point I. The suspension of the traverse ring I4 at I ismovable but not adjustable. 'The traverse ring I4 is connected to afork-shaped end I! of a guide member or rod I5 by means of aself-aligning ball bearing I9 and a trunnion I8 as shown in Figs. '3 and4. The other end of the rod I5 is connected at I6 to a fixed bracketwhich is rigidly attached to some part of the areoplane such as themotor for propelling the plane. Said bearing! 9 is mounted in the eye ofthe traverse ring I4 so that the traverse ring can be turned around twoperpendicular axes with'respect to the guide member I5. The traversering I4 can be swung around the suspension at I by mean of theadjustment spindle 2I connected at II, thus producingthe adjustingmotion. A self-aligning ball bearing .thesecond ring is mounted on theother side of the ball bearing 24 and screwed together with the nut 23.The' free end of the spindle 2I is provided with a safety-and-stop ring29. Displaced by in relation to the suspension points I and II. thetraverse ring I4 carries 'tr'unnlons 30 and 3| (Fig. 4), betweenwhichrests the supporting ring 32'for the ball bearing 33. The inner ring 34of the bearing 33 is mounted on the adjustment sleeve I3, being forcedagainst the stop 36 of the adjustment ring II] by Ineansofa threadedring 35. Another threaded :;rin g- 3l which is screwed intothesupporting ri'ng '32 helps to hold. the outer ring of the ball bean ingwithin the supporting ring. A key 38;.engaging in a suitably dimensionedslot of the sliding bushing 8 prevents the adjustment sleeve In fromturning with relation 17118 bushing B.

Instead of the Cardan-like connection by pro vision of self-aligningball bearings betweenthe traverse. ring I4 and the guide member --I5Taswell a the spindle 2i, the traverse ring .can also be connectedCardan-like or gimbal-fashion with the adjustment sleeve or with thesupporting ring 32 of the ball bearing 33 bymeans'ofan auxiliary ring32* (Fig. 5). This ring. 32" can be swung around the trunnions 3t! and3|, while the supporting ring 32 can be swung perpendicg I runnions 30and 3 I' g ularly thereto aroundthe t of the ring 32. 1

When in operation the propeller revolves around the propeller .or motoraxis III- III jointly with the hollow shaft 4,.the antifriction bushing8 mounted thereon, the adjustment sleeve I0 and the inner ring 34 of theball bear ing 33, with relation to the outer ring of the ball bearingand the remaining parts of the adjustment traverse. 'The position orpitch of the propeller blades is dependent upon the axial position ofthe adjustment sleeve I0, and consequently upon the position of. the nut23 on the spindle 2| which can be turned in the self-aligning ballbearing 22 by means of a Cardan drive 40, as indicated by the brokenline on Fig. 3. Rotation of the spindle 2I cause the nut 23 to be movedaxially and, since the latter is fixed immovably in the traverse ringI4, it is bound to take along the traverse ring swinging same around thetrunnionIS of the suspension point I. Through this swing movementtheadjustment,

sleeve I0 is moved on the bushing 8 by means of the ball bearing 33adapted to carry an. axial load. This movement is transferred by way ofthe guide members I2 to-the adjusting levers I3 which in turn take alongthe propeller blades and cause them to turn in their bearings.

Owing to the Cardan-like or gimbal'mo'unting of the traverse ring bymeans of self-aligning ball bearings, all parts'of the adjustment devicecan follow up any possible skewingwhichmight emanate from the forcestaking effectdu u ing the flight, so that premature wear and tear of theadjustment sleeve ID or the bushing 8, will be largely avoided. Bymanufacturing the sliding bushing 8 from synthetic material it ispossible to preclude any appreciable wear even in continuous operation.It is contemplated within the purview of this invention that theantifriction bushing 8 as well as the adjustment sleeve ID or either ofsaid parts may be made of resin-impregnated fabric or any similarmaterial.

The adjustment of the propeller blade is accomplished, as describedabove, by turning the threaded spindle 2| by means of the indicatedCardan drive member 48, which can be done manually, mechanically orelectrically. In place of an electric drive with rotating screw spindlea hydraulic drive can also be employed.

The present invention has been described in detail with reference tospecific embodiments. It is to be understood, however, that theinvention is not limited by such specific reference but is broader inscope and capable of other embodiments than those specifically describedand illustrated in the drawings.

I claim:

In an adjustable pitch propeller for aircraft, the combination of apropeller hub; propeller blades mounted in said hub to be adjustablyrotated about their longitudinal axes; a propeller shaft on which saidhub is rigidly mounted; a sleeve mounted coaxially and slidably on saidshaft; mean operatively connecting said sleeve with said blades andadapted to rotate said blades upon axial movement of said sleeve; afixed bracket; a link pivoted at one end on a horizontal pivot pin insaid bracket, and having a fork at its other end; a traverse ringdisposed about said shaft; a ball-bearing having its outer race pivotedin said traverse ring for movement about an axis transverse to the axisof the shaft, and its inner ring fixed about said sleeve; a boss on saidring; a self-adjusting ball bearing in said boss; a trunnion in the forkof the link, on which said ball bearing is mounted, the link and ringbeing so connected by the ball bearing that the ring is capable ofmovement about two axes perpendicular to the axis of the link; a secondfixed bracket; a second self-adjusting ball bearing mounted in saidsecond fixed bracket; a rotatable, threaded spindle journaled in saidsecond ball bearing; means for rotating said spindle; a

nut threaded on said spindle; and a third selfadjusting ball-bearingmounted in said traverse ring diametrically opposite to the said bos andin which said nutis carried, the spindle and traverse ring being sorelated that when the spindle is rotated the traverse ring is movedabout one of the axes perpendicular to the axis of the link, to slidesaid sleeve axially of the propeller shaft, cause the link to pivotabout the first fixed bracket, and cause the spindle to pivot about thesecond fixed bracket.

ROBERT PRAUSE.

